Amphibious vehicle

ABSTRACT

Amphibious vehicle has at least one system which is actuated or has its mode of operation changed when the vehicle changes from land mode to water mode or vice versa. The vehicle comprises sensor means which produce an output signal which varies in relation to the proportion of the mass of the vehicle which is buoyantly supported by a body of water. The sensors may sense the position of a wheel relative to the body of the vehicle. This may be achieved by checking the position of a suspension member. The sensor means may comprise a linear sensor or a rotary sensor. The sensor may comprise a potentiometer. Control means may average the output of the sensor over time. Where several sensors are used, control means may process output signals from each sensor to provide an overall output signal. A water presence sensor, such as a thermistor, may be used to provide a second control signal.

BACKGROUND OF THE INVENTION

The present invention relates to an amphibious vehicle which is adapted for use both on land and on water. In particular, the present invention relates to an amphibious vehicle having systems which need to be activated or have their mode of operation changed when the vehicle leaves land and enters water or vice versa.

Known amphibious vehicles often comprise systems which must be actuated or have their mode of operation changed when the vehicle changes from a land use mode to a water borne mode or visa versa. For example, it is known to provide amphibious vehicles with wheels and associated suspension assemblies which can be moved from a protracted position, in which they support the vehicle for land use, to a retracted position, in which the wheels are moved above the water line for use of the vehicle in water. Such an amphibious vehicle is known for example from European patent No. EP 0 742 761. When the vehicle leaves land and enters a body of water, it is necessary for the wheel retraction system to be actuated. However, it is essential that the wheel retraction system is not operated before the vehicle is in a sufficient depth of water that the mass of the vehicle can be supported by the water when the wheels are fully retracted. Similarly, when leaving the water, it is important that the vehicle be in a sufficient depth of water that the wheels can be fully lowered.

In certain known amphibious vehicles it is necessary for the driver to assess the depth of water and to make a judgment as to when it is safe to operate the wheel retraction system. This arrangement has a number of drawbacks. For example, it is possible for the driver to make an error in judging the depth of the water. This may result in the wheels being retracted while the vehicle is still in relatively shallow water such that the vehicle bottoms out as the wheels are retracted. Furthermore, it is not possible for the vehicle to make a smooth transition from land use to water use, as it is necessary for the driver to continually check the depth of the water prior to operating the wheel retraction system.

Several previous approaches have been made to this problem. Aquastrada have filed U.S. Pat. Nos. 5,590,617; 5,570,653; and 5,562,066. In each of these patents, a retractable suspension is allowed to raise the vehicle wheels once a water presence sensor has detected water on the lower hull. Westphalen (U.S. Pat. No. 4,241,686) uses a float switch which must be actuated before a wheel retraction system can be actuated. Bartlett (U.S. Pat. No. 3,903,831) discloses an on-off switch 302 which is actuated when the weight of the vehicle moves off the front wheels, indicating that the vehicle is afloat. However, the position and operation of the switch 302 is not clearly described or illustrated.

Each of these methods has fundamental drawbacks. Aquastrada's water presence sensor could be fooled by the vehicle fording rivers, by water splashed up from puddles, or by body surface water—either rain or during vehicle washing. Any sensor on the outside of the vehicle body is potentially subject to mechanical damage, and could be bridged by marine debris. Furthermore, a single sensor (Aquastrada do not disclose its position) does not ensure that the entire vehicle is afloat. Grounding or grit ingestion into the water jet drive may occur if the water jet is activated when the vehicle is only partly submerged. Westphalen's float switch is liable to delayed action, and to blockage or seizure through ingress of debris. All of these switches are on-off switches, with no intermediate positions offering discrete electrical values.

It is an objective of the present invention to provide an improved amphibious vehicle which overcomes or at least significantly reduces the disadvantages of the known amphibious vehicles.

SUMMARY OF THE INVENTION

Thus, in accordance with a first aspect of the present invention, there is provided an amphibious vehicle adapted for use on land and on water, the vehicle having at least one system which is actuated or has its mode of operation changed when the vehicle changes from a land use mode to a water borne mode or vice versa, characterised in that the vehicle further comprises sensor means adapted such that in use it produces an output signal which varies in relation to the proportion of the mass of the vehicle which is buoyantly supported by a body of water. In accordance with a second aspect of the invention, there is provided an amphibious vehicle having a body, and a plurality of wheels, each wheel being connected to the body of the vehicle by a respective suspension assembly so as to be movable relative to the vehicle body, characterised in that the vehicle further comprises at least one sensor, the or each sensor being adapted to monitor the position of a corresponding wheel relative to the vehicle body and to produce an output signal which varies in relation to the position of the wheel relative to the vehicle body, and a control adapted to process the or each sensor output signal such that, in use, the control provides an overall output signal which varies in relation to proportion of the mass of the vehicle which is buoyantly supported by a body of water in which the vehicle is operating

In accordance with a third aspect of the invention, there is provided an amphibious vehicle having a body, and a plurality of wheels, each wheel being connected to the body of the vehicle by a respective suspension assembly so as to be movable relative to the vehicle body, characterised in that the vehicle further comprises at least one sensor adapted to produce an output signal which varies in relation to the load supported by a respective wheel and its associated suspension assembly as the vehicle enters a body of water.

In an amphibious vehicle in accordance with any of the above aspects of the invention, the output signal from the sensing means can be used to control the actuation or change of use of a system of the vehicle as the vehicle converts between a land use and a water borne mode of operation.

Other features of the invention are discussed hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a front view of an amphibious vehicle in accordance with the invention on land;

FIG. 2 is a view similar to that of FIG. 1 showing the amphibious vehicle in water;

FIG. 3 is a front view of a simplified suspension system of the amphibious vehicle of FIG. 1; and

FIG. 4 is a rear view of the vehicle of FIGS. 1 and 2, shown on water.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 show an amphibious vehicle, indicated generally at 10. The vehicle has wheels 11, each of which is mounted to a vehicle body 12 by means of a respective suspension assembly 13. Although only two wheels 11 are shown in FIG. 1, it will be understood that in a preferred embodiment, the vehicle has four wheels, two at the front and two at the rear, as shown in FIG. 4. However, the precise number of wheels on the vehicle is not essential to the invention.

In FIG. 1, the vehicle is on land with all the vehicle mass being supported by the suspension. The wheels 11 are at their normal relative position with respect to the vehicle body 12.

FIG. 2 shows the amphibious vehicle in water of a depth “D”. As the vehicle 10 enters the water, the mass of the vehicle becomes partially supported by the buoyancy of the hull 14 (as indicated by the arrows), reducing the load on the vehicle suspension. As the depth of the water increases, the proportion of the mass of the vehicle supported by buoyancy increases and the body 12 tends to lift relative to the wheels 11. By sensing the position of the wheels 11 relative to the vehicle body 12, an accurate estimate of the proportion of the mass of vehicle which is buoyantly supported by the water can be obtained. Looked at another way, monitoring the position of a wheel relative to the vehicle body can be used to sense the load supported by the wheel and its associated suspension assembly. When the wheel is fully unloaded, this can be used as an indication that the vehicle is afloat.

Sensing of the position of one of the wheels 11 relative to the vehicle body 12 can be done in various ways. FIG. 3 illustrates one such method in which the position of a component of the wheel's respective suspension assembly 13 is monitored.

FIG. 3 shows a simplified suspension assembly 13 for an amphibious vehicle. The suspension assembly 13 comprises a wheel-support upright 15 to which a wheel 11 is mounted via a stub axle 16. The wheel-support upright 15 is movably attached to the body 12 of the vehicle by means of a lower control arm 17 and an upper control arm 18. Lower control arm 17 is pivotally connected to the vehicle body 12 by an inner bearing means 19 and pivotally connected to the wheel-support upright by an outer bearing means 20. Similarly, upper control arm 18 is pivotally connected to the vehicle body 12 by an inner bearing means 21 and pivotally connected to the wheel-support upright by an outer bearing means 22. The arrangement is such that the angular position of the lower and upper control arms 17, 18 relative to the vehicle body 12 varies as the wheel 11 moves relative to the vehicle body.

Two alternative sensor arrangements 23, 24 are shown, either of which can be used to monitor the angular position of one of the control arms 17, 18 relative to the vehicle body 12. In both arrangements, the sensor 23, 24 is in the form of a potentiometer, which produces an output signal which varies with sensor travel.

In a first arrangement, a linear sensor 23 is connected between one of the arms, in this case the lower control arm 17, and the vehicle body 12. Movement of the wheel 11 relative to the vehicle body 12 will cause the lower control arm 17 to pivot about its inner bearing means 19. This movement is detected by the sensor 23 which produces an output signal indicative of the angular position of the lower control arm 17 relative to the body and so indicative of the vertical position of the wheel relative to the body.

In a second, alternative, sensor arrangement, a rotary sensor 24 is connected between one of the control arms, in this case the upper control arm 18, and its inner bearing means 21. Movement of the wheel 11 relative to the vehicle body 12 will cause the upper control arm 18 to pivot about its inner bearing means 21. This movement is detected by the sensor 24 which produces an output signal indicative of the angular position of the upper control arm 18 relative to the body and so indicative of the vertical position of the wheel relative to the body.

The sensors 23 or 24 provide an output signal which is indicative of the position of the wheel 11 relative to the vehicle body 12. If this output signal is averaged over time, it is possible to distinguish between the normal movement of the wheel when the vehicle is driven on land from the relative suspension movement between the wheel and the vehicle body which results from an increasing proportion of the vehicle's mass being buoyantly supported as the vehicle enters a body of water.

It can be seen then that the time averaged output signal of the sensors provides an indication of the proportion of the mass of the vehicle which is buoyantly supported by the water. This output signal can be used to control the actuation or change of use of various systems of the vehicle when the vehicle is being converted between land use and water borne modes. For example, when the vehicle enters a body of water, the output signal can be used to determine when a given proportion of the mass of the vehicle is buoyantly supported such that it is safe for the wheel retraction system to be operated to retract the wheels. Alternatively, when the vehicle is preparing to leave the water, the output signal can be used to determine when sufficient of the vehicle's mass is being supported by the road wheels such that power from the engine can be safely diverted to the driving wheels to propel the vehicle out of the water.

The output signal of the sensor means can be arranged to vary linearly in relation to the proportion of the mass of the vehicle which is buoyantly supported. Alternatively, the relationship between the output signal and the proportion of the mass of the vehicle which is buoyantly supported may be non-linear. Where the relationship is non-linear, the output signal may require analysis through mapping techniques, which are known from, for example, internal combustion engine control software.

It will be apparent that the sensing arrangements described above are only examples of a number of possible ways in which the position of a wheel relative to the vehicle body could be monitored. For example the linear sensor 23 could be connected between the upper control arm 18 and the vehicle body, or the rotary sensor 24 could be connected between the lower control arm 17 and its inner bearing means 19. Indeed sensors could be used to monitor the movement of any convenient component of the suspension or even of the wheel itself For example, sensors could be mounted to an anti-roll bar, track control arm or to a trailing or a semi-trailing arm.

Sensing may take place in respect of one or more wheels of the vehicle. It is preferred, however, that the position of at least two or more of the wheels is monitored relative to the vehicle body and that the output signals from all the sensors are processed to produce an overall output signal indicative of the proportion of the mass of the vehicle which is buoyantly supported.

Where sensing is carried out in respect of more than one wheel, the outputs from the various sensors can be averaged so that the effects of prolonged cornering or of the inclination of the ground can be taken into account. In this respect, the outputs from sensors related to wheels on either side of the vehicle can be averaged to take into account the effects of prolonged cornering, as may occur when going down a spiral ramp for example. Similarly, the outputs of sensors associated with wheels at the front and rear of the vehicle can be averaged to take into account the effect of the vehicle being on an incline such as a ramp into the water.

It should be understood, however, that the invention is not limited to arrangements for monitoring the position of the wheels relative to the body as a means of determining the proportion of the vehicle's mass which is buoyantly supported. In an alternative arrangement, for example, load sensors or strain gauges could be applied to components of the suspension assembly as a means of monitoring the load supported by the suspension. As the proportion of the mass of the vehicle which is buoyantly supported increases, the load on the components of the suspension assembly will tend to decrease or vary, say, from a compressive load to a tensile load. In a further alternative arrangement, a pressure sensor could be used to sense the pressure of hydraulic fluid in a suspension strut as a means of sensing the load supported by the suspension assembly and hence the proportion of the mass of the vehicle which is buoyantly supported.

It will be noted that in all the embodiments described above, the sensors are potentiometers, having continuous electrical contact with an output related to sensor travel; as opposed to being on-off switches, whose output has a step change, from “on (full voltage)” to “off (zero voltage)”.

The use of continuous contact potentiometers has several advantages over simple on-off switches. In any mechanical assembly, there will be a build-up of tolerances in series production, so that dimensions which are fixed at the design stage will vary in practice. As a vehicle is used, components will settle into both absolute and relative positions which may again vary from the design nominal value. If an on-off switch is used, it may never reach the position in which the output changes as required, from “on” to “off” or vice versa. A continuous contact sensor, however, will vary its output even with a small change in input. Hence, such a sensor will be more reliably functional in series production, and when a vehicle is in use; as opposed to the relatively controlled prototype or one-off build phase, and subsequent testing by the vehicle builder in a controlled environment.

Further, if an on-off switch fails in service, its change in output may be taken as a signal output. Fault tolerant software can be developed to get around this problem; but a continuous contact sensor will only produce a zero voltage if it is faulty. This makes fault diagnosis easier. Simpler software is generally more reliable, and is of course cheaper to develop. Development costs are crucial in a low volume field such as amphibious vehicles. On the other hand, “smart” software may be used with continuous contact sensors to detect other sensor system failure modes, such as a fractured linkage; which would give a sensor output within limits, but unchanging.

Also, if an amphibious vehicle having an independent suspension system is resting with one or two wheels supported by ground under water, it may be safe to raise the wheels. A logic circuit using on-off switches would find this a much more difficult problem to solve than a logic circuit using continuous contact sensors, which could average signals to determine a safety margin. The worst scenario with on-off switches is of course for only the non-driven road wheels to be supported on ground under water, which would make further progress difficult; as diversion of power to driven road wheels would result in minimal vehicle movement. It is acknowledged that even a continuous contact sensor could be momentarily fooled by the vehicle weight coming off the suspension over a crest in a road, for example a “hump back” bridge; but this would be a very brief input in timing terms. The vehicle configuration would be protected by timing devices in the control logic circuit.

Continuous contact sensors also offer more adaptable logic than on-off switches. It may be found that it is acceptable to raise vehicle wheels when, say, ten per cent, or twenty per cent of the vehicle weight is supported by the suspension. This will be easier to arrange by setting a threshold for the sensor output signal (which could be a voltage, current, or capacitance, for example), as opposed to (inter alia) fixing a limit switch on a strut somewhere before the end of the strut travel.

For safety's sake, it may be preferred that the wheels of an amphibious vehicle are retracted only when substantially 100% of the vehicle's mass is buoyantly supported, i.e. when the vehicle is fully afloat. However, even where the threshold is set at or around 100%, the use of proportional sensing means has many of the advantages discussed above when compared with the use of simple on-off switches. Furthermore, different thresholds could be set for different systems. For example, whilst wheel retraction may not be permitted until the vehicle is fully afloat, the depth sensing system could be used to initiate transfer of drive to a marine propulsion means when the vehicle is only partially afloat, say when 50% to 60% of the vehicle's mass is buoyantly supported.

The output signal can be used in a number of ways to control the use or actuation of various systems on the vehicle. The signal could be used for example to provide a visual or audible indication to the driver or operator of the vehicle when it is safe to operate various systems on the vehicle required to change the vehicle from a land mode to a water borne mode or vice versa. For example, the driver would know that it was safe to actuate a wheel retraction system or to transfer the torque produced by the vehicle's engine from the wheels to a water propulsion means such as a water jet.

The output signal could also be used to automatically actuate vehicle systems required to convert the vehicle from land use mode to water borne mode or vice versa, as the vehicle enters or leaves the water. As an example, control means can be provided such that the output signal is used to trigger automatic actuation of a wheel retraction system as the vehicle enters the water and reaches a depth in which it is safe for the wheels to be retracted.

In a particularly preferred embodiment, a secondary sensor means is used to confirm that the vehicle is in a sufficient depth of water. This secondary sensor means may take the form of a water presence sensor appropriately mounted on the outside of the hull of the vehicle, such that the sensor is immersed when the vehicle is afloat. In this arrangement, the control means is adapted such that it will only permit the actuation, or change of mode, of a system of the vehicle when both the primary output signal indicative of the proportion of the mass of the vehicle which is buoyantly supported and the secondary signal from the water presence sensor indicate that it is safe to do so.

Such an arrangement is illustrated in FIG. 4, which shows a rear view of the vehicle 10 afloat in water. Proportional sensors are used to monitor the position of each of the front wheels of vehicle relative to the body as described above with respect to FIGS. 1 to 3. The output signals from the sensors associated with each of the front wheels are processed to produce an overall output signal indicative of the load supported by the suspension assemblies of the front wheels and hence of the proportion of the mass of the vehicle which is buoyantly supported, the primary signal. A water presence sensor 33 is mounted to the rear of the vehicle hull 14 just above the water jet outlet 34. The water presence sensor 33 produces an output signal when it is immersed in water, indicating that the rear of the vehicle is afloat. The control system (not shown) will allow the wheels of the vehicle to retracted only when the overall output signal from the wheel position sensors indicates that the front of the vehicle is afloat, e.g. when the suspension assemblies of the front wheels are unloaded or drooped, and when it receives a signal from the water presence sensor 33 indicating that the rear of the vehicle is also afloat. This ensures that both ends of the vehicle are in the water before the wheels retract.

The use of a secondary sensor means to confirm that the vehicle is afloat in this way helps to avoid inadvertent actuation of the wheel retraction, or other system, due to the control system being fooled by extreme conditions acting on the suspension system of the vehicle. The water presence sensor 33 can be of any suitable type, such as a thermistor. The actual positioning of the water presence sensor 33 on the vehicle hull 14 will depend on the particular design of the vehicle and its method of use. Positioning the water presence sensor at the back of the hull is preferable for a vehicle capable of planing and which has a rearward weight bias.

Whilst a water presence sensor mounted to the outside of the hull is the preferred arrangement for providing a secondary sensor signal, other systems could be used. For example, the secondary signal could be provided by means of a reflected signal system such as sonar, radar, lidar, etc. Such a system could bounce a signal from an emitter/receiver unit on the body of the vehicle to a movable object such as a wheel, in which case, the emitter/receiver unit can conveniently be mounted under the wing of the vehicle.

Whereas the invention has been described in relation to what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed arrangements but rather is intended to cover various modifications and equivalent constructions included within the spirit and scope of the invention as defined by the claims. 

1. An amphibious vehicle adapted for use on land and on water, the vehicle having at least one system which is actuated or has its mode of operation changed when the vehicle changes from a land use mode to a water borne mode or vice versa, characterised in that the vehicle further comprises sensor means adapted such that in use it produces an output signal which varies in relation to the proportion of the mass of the vehicle which is buoyantly supported by a body of water.
 2. An amphibious vehicle as claimed in claim 1, in which the sensor means comprises at least one sensor adapted to sense the position of a wheel of the vehicle relative to the body of the vehicle.
 3. An amphibious vehicle according to claim 2, in which the wheel is mounted to the vehicle body by a suspension assembly and the at least one sensor is adapted to sense the position of a component of the suspension assembly relative to the vehicle body.
 4. An amphibious vehicle according to claim 3, in which the at least one sensor comprises a linear sensor connected between a component of the suspension assembly and the vehicle body.
 5. An amphibious vehicle according to claim 3, in which the at least one sensor comprises a rotary sensor connected between the suspension component and a point about which the component pivots as the wheel moves relative to the vehicle body.
 6. An amphibious vehicle according to claim 4 in which the at least one sensor means comprises a potentiometer, whose output signal is related to sensor travel.
 7. An amphibious vehicle according to any claim 2 in which the sensor means comprises control means adapted to average the output signal of the at least one sensor over time.
 8. An amphibious vehicle according to claim 2 in which the sensor means comprises at least two sensors, each sensor being adapted to provide an output signal representative of the position of a respective wheel of the vehicle relative to the body of the vehicle, and control means adapted to process the output signals of each of the sensors to provide an overall output signal indicative of the proportion of the mass of vehicle which is buoyantly supported by a body of water.
 9. An amphibious vehicle according to claim 8, in which control software is used to analyse signals from different sensors and to determine acceptable mismatch situations.
 10. An amphibious vehicle according to claim 9, in which the control software is fault tolerant.
 11. An amphibious vehicle according to claim 1 in which the vehicle further comprises control means adapted to activate or to change the mode of use of the at least one system in response to the output signal of the sensor means.
 12. An amphibious vehicle having a body, and a plurality of wheels, each wheel being connected to the body of the vehicle by a respective suspension assembly so as to be movable relative to the vehicle body, characterised in that the vehicle further comprises at least one sensor, the or each sensor being adapted to monitor the position of a corresponding wheel relative to the vehicle body and to produce an output signal which varies in relation to the position of the wheel relative to the vehicle body, and a control adapted to process the or each sensor output signal such that, in use, the control provides an overall output signal which varies in relation to proportion of the mass of the vehicle which is buoyantly supported by a body of water in which the vehicle is operating.
 13. An amphibious vehicle as claimed in claim 1, in which a system of the vehicle is actuated or has its mode of use change only when the output signal indicates that substantially 100% of the vehicle's mass is buoyantly supported.
 14. An amphibious vehicle having a body, and a plurality of wheels, each wheel being connected to the body of the vehicle by a respective suspension assembly so as to be movable relative to the vehicle body, characterised in that the vehicle further comprises at least one sensor adapted to produce an output signal which varies in relation to the load supported by a respective wheel and its associated suspension assembly as the vehicle enters a body of water.
 15. An amphibious vehicle as claimed in claim 1, in which the output signal comprises a primary output signal and the vehicle comprises a further sensor means for producing a secondary output signal indicative that the vehicle is in water.
 16. An amphibious vehicle as claimed in claim 15, further comprising a control system adapted to monitor the primary and secondary output signals and to actuate, or change the mode of use of, a system of the vehicle when both the primary and secondary output signals indicate that the vehicle is afloat.
 17. An amphibious vehicle as claimed in claim 15 in which the further sensor means comprises a water presence detector.
 18. An amphibious vehicle as claimed in claim 17, in which the water presence detector comprises a thermistor.
 19. (canceled) 